The disclosure of Japanese Patent Application No. 2000-379161 filed on Dec. 13, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a fluid-filled vibration damping device, which is adapted to provide vibration damping effect on the basis of flows of a non-compressible fluid filling a fluid chamber formed therein, and which is suitably used as an engine mount, a body mount and the like for an automotive vehicle.
2. Description of the Related Art
As one type of a vibration coupling or bushing interposed between two members of a vibration system, there is known a fluid-filled vibration damping device. A known example of such a fluid-filled vibration damping device is disclosed in JP-A-9-257090 and JP-A-10-38016, wherein the vibration damping device includes: a first mounting member connectable to one of the two member of the vibration system, and a second mounting member having a generally cup shape and connectable to the other member of the vibration system, said second mounting member being opposed at its open end portion to the first mounting member with an axial spacing therebetween; an elastic body interposed between and elastically connecting the first and second mounting members such that an opening of the second mounting member is fluid-tightly closed by the elastic body, to thereby partially define a pressure receiving chamber on one of opposite sides thereof, which is filled with a non-compressible fluid and located within an interior space of the second mounting member; an elastic rubber layer extending between the first and second mounting member and disposed outward of the elastic body with a spacing therebetween, so as to partially define an equilibrium chamber on the other side of the elastic body remote from the pressure receiving chamber, which is filled with the non-compressible fluid; and an orifice passage for fluid communication between the pressure receiving chamber and the equilibrium chamber.
Upon application of a vibrational load between the first and second mounting members in an axial direction of the vibration damping device in which the first and second mounting member are moved toward and away from each other, a pressure of the fluid in the pressure receiving chamber varies due to an elastic deformation of the elastic body, thus causing a fluid-pressure difference between the pressure receiving chamber and the equilibrium chamber whose volume is variable due to an elastic deformation of the elastic rubber layer. This fluid pressure difference between the pressure receiving chamber and the equilibrium chamber forces the fluid to flow through the orifice passage between the two chambers, so that the fluid-filled vibration damping device exhibits a desired vibration damping effect on the basis of resonance or flows of the fluid flowing through the orifice passage.
In the disclosed fluid-filled vibration damping device, moreover, the pressure receiving chamber is formed in a space interposed between the first and second mounting members, while the equilibrium chamber is disposed radially outwardly of the first mounting member. This arrangement makes it possible to decrease an axial distance between the first and second mounting member, thus effectively minimizing a size of the vibration damping device in its axial direction, while effectively locating an elastic center of the vibration damping device in a relatively lower side of the device. For these advantages, such a known fluid-filled vibration damping device has been employed as an engine mount of the vehicle or the like.
Since the fluid-filled vibration damping device exhibits the desired vibration damping effect on the basis of the resonance or flows of the fluid flowing thought the orifice passage, a vibration damping characteristics of the vibration damping device is effectively tuned by suitably adjusting a length and a cross-sectional area of the orifice passage.
However, the known fluid-filled vibration damping device disclosed in the above-indicated publications suffers from a low degree of freedom in designing the length and cross sectional area of the orifice passage and a resultant difficulty in changing its design. That is, the known fluid-filled vibration damping device suffers from inherent problem, i.e., a low degree of freedom in tuning its vibration damping characteristics.
It is therefore one object of this invention to provide a novel fluid-filled vibration damping device which is compact in size with a reduced axial distance between a first mounting member and a second mounting member, and which enables to increase a degree of freedom in tuning an orifice passage thereof with a simple structure.
It is another object of this invention to provide a method of producing with ease a fluid-filled vibration damping device which is compact in size with a reduced axial distance between the first mounting member and the second mounting member, and which ensures an increased degree of tuning of the orifice passage thereof.
The above and/or other objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to those modes of the invention and combinations of the technical features, but may otherwise be recognized based on the thought of the present invention disclosed in the whole specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A fluid-filled vibration damping device comprising: (a) a first mounting member; (b) a second mounting member having a generally cup shape and being opposed at an open end portion to the first mounting member with a given spacing therebetween; (c) an elastic body interposed between and elastically connecting the first and second mounting members such that the open end portion of the second mounting member is fluid-tightly closed by the elastic body; (d) a pressure receiving chamber partially defined by the elastic body and formed within the second mounting member on one of opposite side of the elastic body, the pressure receiving chamber being filled with a non-compressible fluid; (e) an elastic rubber layer extending between the first and second mounting members and disposed outward of the elastic body with a spacing therebetween; (f) an equilibrium chamber partially defined by the elastic rubber layer and formed on an other one of the opposite sides of the elastic body, the equilibrium chamber being filled with the non-compressible fluid; (g) an outer circumferential metallic sleeve having a generally cylindrical shape and bonded to an outer circumferential surface of the elastic body upon vulcanizing a rubber material for forming the elastic body, the outer circumferential metallic sleeve including an outward flange portion integrally formed at one of axially opposite ends thereof located on a side of the open end portion of the second mounting member, so as to extend radially outwardly; (h) a cylindrical orifice member disposed radially outwardly on the outer circumferential metallic sleeve with one of axially opposite end faces thereof superposed on one of axially opposite surfaces of the outward flange portion of the outer circumferential metallic sleeve which is remote from the open end portion of the second mounting member, the orifice member together with the outer circumferential metallic sleeve being fitted into a cylindrical wall portion of the second mounting member so that the orifice member is interposed between the outer circumferential metallic sleeve and the cylindrical wall portion of the second mounting member to define therebetween an orifice passage for fluid communication between the pressure receiving chamber and the equilibrium chamber; (i) an outer metallic ring bonded to an outer peripheral portion of the elastic rubber layer upon vulcanization of a rubber material for forming the elastic rubber layer, the outer metallic ring being superposed on an other one of the axially opposite surfaces of the outward flange portion of the outer circumferential metallic sleeve, while being fixedly fitted into the cylindrical wall portion of the second mounting member.
In the fluid-filled vibration damping device constructed according to this mode of the invention, the orifice member is interposed between the outer circumferential metallic sleeve and the cylindrical wall portion of the second mounting member. Since a configuration of the orifice passage can be defined by the orifice member, a length and a cross-sectional area of the orifice passage can be designed with a high degree of freedom, and can be changed with ease. For instance, a vibration damping characteristics of the fluid-filled vibration damping device can be change by simply changing the orifice member.
Further, the orifice member is disposed radially outwardly of the elastic body, so that the orifice member can be assembled in the vibration damping device without increasing a size of the vibration damping device in its axial direction. Thus, the fluid-filled vibration damping device is surely made compact in size in its height dimension.
In the fluid-filled vibration damping device of this mode of the invention, the orifice member, the outer circumferential metallic sleeve and the outer metallic ring are superposed one another in the axial direction thereof. In this arrangement, the outer metallic ring is fixed to the second mounting member with high strength, thus ensuring a firm fixing of the orifice member and the outer circumferential metallic sleeve as well as the outer metallic ring with respect to the second mounting member, with high strength. Thus, the fluid-filled vibration damping device of this mode of the invention enables with ease to assemble the outer metallic ring, the orifice member and the outer circumferential metallic sleeve with respect to the second mounting member, with high stability and with a simple structure.
(2) A fluid-filled vibration damping device according to the above-indicated mode (1) of the invention, wherein the orifice member is superposed at an other one of the axially opposite end faces thereof on a side of a bottom wall portion of the second mounting member, and includes an annular protrusion integrally formed at the other one of the axially opposite end faces thereof so as to protrude radially inwardly, wherein the elastic body is held in abutting contact at an end face of an outer peripheral portion thereof on the annular protrusion, and wherein the annular protrusion is formed with a first communication passage through which one of opposite ends of the orifice passage is held in fluid communication with the pressure receiving chamber.
In this mode of the invention, the first communication passage serving as an opening of the orifice passage to the pressure receiving chamber is formed in the orifice member. In comparison with the case where the first communication passage is formed in the elastic body or the outer circumferential metallic sleeve, the vibration damping device of this mode is able to eliminate a need for positioning the orifice passage with respect to the first communication passage, thus ensuring an improved efficiency of assembling of the orifice member.
Further, an axial dimension or thickness of the annular protrusion of the orifice member may be changed to adjust the axial dimension of the outer peripheral portion of the elastic body. This makes it possible to adjust a spring characteristics of the elastic body and the vibration damping device.
(3) A fluid-filled vibration damping device according to the above indicated mode (2) of the invention, wherein the first communication passage has a tunnel form extending through the annular protrusion or a groove form open to the bottom surface of the second mounting member, and the outer circumferential metallic sleeve is fluid-tightly superposed on the annular protrusion over an entire circumference thereof in an axial direction thereof with the elastic body interposed therebetween.
In this mode of the invention, the outer peripheral portion of the elastic body is fluid tightly held in abutting contact with the annular protrusion over its entire circumference. This arrangement is effective to prevent a leakage of the fluid through a clearance formed between the outer circumferential metallic sleeve and the orifice member and a resultant shortening of the orifice passage. Therefore, the fluid-filled vibration damping device of this mode of the invention is capable of exhibiting a desired damping effect with high stability.
A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(3), wherein the orifice member includes a first communication passage for fluid communication of one of opposite ends of the orifice passage with the pressure receiving chamber, and a second communication passage for fluid communication of an other one of the opposite ends of the orifice passage with the equilibrium chamber.
In this mode of the invention, both of the first and second communication passages serving as openings of the orifice passage with respect to the pressure receiving chamber and the equilibrium chamber are formed in the orifice member. In comparison with the case where the first and second communication passages are formed in the elastic body and/or the outer circumferential metallic sleeve, the vibration damping device of this mode eliminates a need for positioning of the orifice member with respect to the elastic body and the outer circumferential metallic sleeve in a circumferential direction thereof. This arrangement permits a further improved efficiency of assembling of the orifice member.
(5) A fluid-filled vibration damping device according to the above-indicated mode (4) of the invention, wherein the outward flange portion of the outer circumferential metallic sleeve has a plurality of windows formed therethrough and spaced apart from each other in a circumferential direction thereof, such that the second communication passage is held in fluid communication with the equilibrium chamber through any one of the window irrespective of a circumferential position of the orifice member relative to the outer circumferential metallic sleeve.
The arrangement of this mode of the invention makes it possible to form the second communication passage, i.e., the opening of the orifice passage to the equilibrium chamber, substantially only in the orifice member, even in the case where the orifice passage is connected to the equilibrium chamber on the side of the one of axially opposite end faces of the orifice member in which the outward flange portion of the circumferential metallic sleeves is placed on the orifice member. This arrangement eliminates a need for positioning the orifice member to the outer circumferential metallic sleeve in the circumferential direction thereof.
(6) A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(5), wherein a bottom wall portion of the second mounting member includes a through hole, and a movable rubber plate is elastically deformably disposed in the through hole such that the through hole is fluid tightly closed by the movable rubber plate.
In this mode of the invention, an elastic deformation of the movable rubber plate functions to reduce or absorb a fluid pressure change of the pressure receiving chamber upon application of a vibrational load within a high frequency band in which a resistance to flow of the fluid through the orifice passage tends to be increased. Therefore, the presence of the movable rubber plate ensures an improved vibration damping effect of the vibration damping device with respect to vibrations having a relatively high frequency and a relatively small amplitude.
(7) A fluid-filled vibration damping device according to the above mode (6), wherein the one of axially opposite end of the orifice member on a side of the bottom wall portion of the second mounting member extends radially inwardly so as to form a stop portion having at least one through hole, the stop portion being located axially inward of the movable rubber plate with a given axial spacing therebetween, so as to limit an amount of displacement of the movable rubber plate in a direction toward an inside of the pressure receiving chamber.
In this mode of the invention, a stopper mechanism for limiting an excessively large amount of displacement of the movable rubber plate toward the inside of the pressure receiving chamber can be provided by utilizing the orifice member, without needing additional member.
(8) A fluid-filled vibration damping device according to the above-indicated mode (6) or (7), further comprising: a covering member superposed on the bottom wall portion of the second mounting member and fixed onto the cylindrical wall portion of the second mounting member, so as to form a protecting part having an air hole and located axially outward of the movable rubber plate with an axial spacing therebetween, the protecting part being adapted to limit an amount of displacement of the movable rubber plate in a direction away from the pressure receiving chamber.
In this mode of the invention, the use of the covering member makes it possible to provide with a simple structure a stopper for limiting an excessively large amount of displacement of the movable rubber plate in the direction away from the pressure receiving chamber, and a cover member for protecting the movable rubber plate from an interference with other components or members.
(9) A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(8) wherein the orifice member includes a circumferential groove open in an outer circumferential surface thereof, and an opening of the circumferential groove is closed by the cylindrical wall portion of the second mounting member, to thereby form the orifice passage.
In this mode of the invention, a length and a cross sectional area of the orifice passage can be easily changed by adjusting the shape or other factors of the grooves. The use of the orifice member arranged as described above makes it easy to form the orifice passage extending along the cylindrical wall portion of the second mounting member with a circumferential length which is larger than an entire circumference of the cylindrical wall portion of the second mounting member. This arrangement ensures a high degree of freedom in tuning a vibration damping characteristics of the fluid-filled vibration damping device. In order to prevent the above-indicated shortening of the orifice passage with high stability, a sealing rubber layer may be bonded to an inner circumferential surface of the cylindrical wall portion of the second mounting member and compressed between the orifice member and the second mounting member, preferably. Yet preferably, the orifice member is press-fitted into the second mounting member, or alternatively is disposed radially inward of the cylindrical wall portion of the second mounting member, and then the cylindrical wall portion is radially inwardly drawn onto the outer circumferential surface of the orifice member, so that the orifice member is held in close contact with the cylindrical wall portion of the second mounting member. Further, the outer circumferential metallic sleeve is bonded by vulcanization to the elastic body and is preferably press-fitted into and radially outwardly forced onto second mounting member so that the outer circumferential metallic sleeve is firmly fixed to the second mounting member.
(10) A fluid-filled vibration damping device according to any one of the above modes (1)-(8), further comprising an inner metallic ring bonded to an inner peripheral portion of the elastic rubber layer upon vulcanizing a rubber material for forming the elastic rubber layer, wherein the metallic fixing member is fixedly fitted onto the first mounting member.
In this mode of the invention, the elastic body and the elastic rubber layer are formed independently of each other. This makes it possible to simplify a structure of a mold for forming the elastic body and the elastic rubber layer, and to facilitate a manufacture of the elastic body and the elastic rubber layer, while permitting to form the elastic body and the elastic rubber layer with different materials, resulting in an increased degree of freedom in designing the fluid-filled vibration damping device of this mode. Moreover, the use of the metallic fixing member enables to firmly fix the inner peripheral portion of the elastic rubber layer to the first mounting member, with a simple assembling operation.
(11) A method of producing a fluid-filled vibration damping device defined in any one of the above modes (1)-(10), comprising the steps of: (i) press-fitting the outer circumferential metallic sleeve bonded to an outer circumferential surface of the elastic body to which the first mounting member is bonded and the orifice member into the cylindrical wall portion of the second mounting member; (ii) press-fitting the outer metallic ring bonded to the elastic rubber layer into the cylindrical wall portion of said second mounting member such that the outer metallic ring is superposed on the orifice member and the outward flange portion of the outer circumferential metallic sleeve in an axial direction thereof; and then (iii) radially inwardly drawing an open end portion of the cylindrical wall portion of the second mounting member so that the outer metallic ring is disassembly firmly fitted into the cylindrical wall portion of said second mounting member.
This method of the invention enables to form the fluid-filled vibration damping device according to the invention with ease, and facilitate assembling of the elastic body bonded to the first mounting member with the second mounting member, which are formed independently of each other. For instance, the assembling of the integral vulcanized assembly of the elastic body, the orifice member, and the elastic rubber layer with respect to the second mounting member may be effected within a mass of a non-compressible fluid, thus facilitating filling the pressure receiving chamber and the equilibrium chamber with the non-compressible fluid.